This invention relates to methods of manufacturing an infrared radiation detector device of cadmium mercury telluride. The invention further relates to detector devices manufactured by such methods.
In a paper entitled "Properties of Ion-Implanted Junctions in Mercury-Cadmium Telluride" by A. Kolodny et al (I.E.E.E. Transactions on Electron Devices, Vol. ED-27, pages 37 to 42) an experimental method of manufacturing a detector device is disclosed. The method comprises the steps of (a) providing a body of cadmium mercury telluride, at least a portion of which has conductivity characteristics of p-type material at the operating temperature of the device, and (b) bombarding at least a part of the surface of the body with ions to convert a part of the body portion into material having conductivity characteristics of n-type material at the operating temperature of the device. In the experimental method the ion bombardment was effected in an ion implantation machine with ion doses of between 10.sup.13 and 10.sup.15 ions per cm.sup.2 at energies of 100 keV to 300 keV to form p-n junctions in the body at a depth which was typically less than 1 micron and which was determined by the implantation depth of the ions in the body.
The effect of implanting different ion species was studied by using argon, boron, aluminium and phosphorus ions. The authors of the paper obtained essentially the same results from the implantation of all these different species and concluded that implantation damage (i.e. lattice defects) adjacent the body surface was the primary cause for converting the p-type cadmium mercury telluride surface to material having n-type characteristics. These experimental results are in conflict with those produced by some other workers in the art and do not appear to provide a readily reproducible method for the manufacture of reliable infrared radiation detector devices on a large scale. Furthermore ion implantation equipment is expensive to purchase and expensive both to house and to maintain fully operational in a manufacturing environment.